Something I feel like I should visit periodically, though I should say it's coming up at the moment because ForceSubsMOS appears to fail if there is an active promo code. I'm working through this with support.
Our usage is that we have a package onsale prior to making our events available for single ticket purchase. So we have to be able to sell packages of events without someone being able to buy the same events individually. Except that if you are buying a package, we want to customers to be able to turn around and buy "Subscription Add-on" tickets to individual events...
This, of course, is easily handled by the ForceSubsMOS, but it does cause a number of other issue, specifically when we want to also apply various donor benefits to people making a package purchase (usually a lot of overlap).